XBB.1.5 an emerging threat: correspondence
Authors: Aroop Mohanty, Ranjana Rohilla, Rachana Mehta, Bijaya Kumar Padhi, Ranjit Sah
Journal: International Journal of Surgery (2023)

Highlights XBB, emerged by recombination of two circulating BA.2 86 lineages, BJ.1 and BM.1.1.1 is labelled as a variant under monitoring by the WHO. It is being stated that XBB.1.5 is a supervariant because it invades human cells via Angiotensin converting enzyme 2 and spreads much faster than old XBB or BQ. XBB has become predominant in India and Singapore and is spreading in several countries. Dear Editor, Omicron (B.1.1.529) has been the principally circulating strain since the end of 2021, but the number of its sublineages is expanding, such as BA.1, BA.2, BA.4, BA.5, and BA.2.75. It has been labelled a 'Variant of concern' by the WHO. As per nomenclature rules devised by the WHO, evolving from a third level-branch of the PANGOLIN (B.1.1.529) phylogeny, other Omicron sublineages should be named with aliases; these lineages occur every fourth branching. For Omicron, BA was the first alias; BA.5 refers to B.1.1.529.5, while BF.1.1 used for BA.1.1.529.5/B.1.1.529.5.3.4.1. The nomenclature is expanding, it is becoming vague to understand the names. After alphabet enervation, letters are added to names (e.g. BW.* for sublineages and XBB for recombinants). XBB, evolved by recombination of two circulating lineages (BA.2 86), that is, BJ.1 and BM.1.1.1 (a descendant of BA.2.75), labelled as a variant under monitoring by the WHO, has now been detected in more than 30 countries worldwide. XBB is found to have a higher risk of reinfection, is most transmissible, and is the most immune-evasive sub lineage known so far1,2. XBB has become predominant in India and Singapore and is spreading in several countries. XBB harbours the S substitutions N460K, R346T, and F486S. It shows a substantially higher Re (effective reproduction number) than the ancestral lineages, suggesting that the recombination has increased its Re. This is the first incidence in which a variant of severe acute respiratory syndrome coronavirus 2 has increased its potential through a recombination event rather than a solitary or random mutation3. XBB.1.5 evolved from XBB, began circulating in the UK in September 2022. At the beginning of December, it accounted for only 4% of cases, so it has quickly surpassed other versions of Omicron. Coronavirus disease (COVID) hospital admissions have been rising recently, and the government has restarted its testing programme. As on 7 December 2022, one in 25 COVID cases in the UK were XBB.1.5. An expert from the eminent 'London School of Hygiene and Tropical Medicine' said it was unlikely that the UK will have major problems as the residents have high levels of vaccination and previous infections4. In the USA, XBB.1.5 was detected in 27% of COVID-19 cases sent for genome sequencing in the first week of January 2023, compared with 18.3% in the last week of December 2022. It is spreading at a rapid speed as compared to other variants of COVID-19. XBB.1.5 is becoming the only omicron subvariant showing noteworthy growth in the USA right now, ranking second after omicron BQ.1.1, which currently earmarks 34% of COVID-19 cases sequenced in the USA5. In India, the SARS-CoV-2 Genomics Consortium (INSACOG) informed that five cases of the XBB.1.5 variant have been detected in Gujarat, Karnataka, and Rajasthan states. The INSACOG has reported that Omicron and its sublineages are becoming dominant variants circulating in India. The latest genomic surveillance data from India show XBB accounts for 20% of all cases, while the older variant BA.2.75 is still dominant. Health experts state that India does not have to worry about XBB.1.5 as more than 90% of its eligible population has been vaccinated, and 30–40% have received booster doses. It is being stated that XBB.1.5 is a supervariant in the context of morphology and pathogenesis as it invades human cells through Angiotensin converting enzyme 2, spreads much faster than previous XBB/BQ, and causes hospitalisations, and it has achieved immune evasiveness by acquiring a rare type of mutation called F486P in its receptor binding domain6. However, keeping in mind that there has been increased travel and holiday gatherings, COVID-appropriate behaviour should be practiced, and booster vaccines along with strong immunity can help fight the infection. This latest variant is a reminder that we have tools and measures to fight COVID and minimise severity and mortality; the vaccines are still protecting against severe disease7–9, and antivirals can still treat infection from XBB.1.5. Appropriate and effective usage of available resources is the need of the hour. Ethical approval Not applicable. Consent Not applicable. Sources of funding No funding received. Author contribution A.M. and R.R. design and draw the original draft. R.M., B.K.P., and R.S. review the literature, critically edit the manuscript. All authors read and approve for the final manuscript. Conflicts of interest disclosure No conflicts of interest. Research registration unique identifying number (UIN) Name of the registry: NA. Unique identifying number or registration ID: NA. Hyperlink to your specific registration (must be publicly accessible and will be checked): NA. Guarantor Ranjit Sah.